Injection cycle time calculation

Hi everybody,

I am looking in calculating (even in a close approx.) the injection cycle of one of my parts.
Considering the plastic ABS or PC-ABS , the wall thickness, the projected area...is it possible to calculate the cycle time?

I googled it...but the information that I was asked for (oil level, etc) were really not possible to guess.

I would appreciate any feedback,

Best regards, Gini

08-10-2014 03:03 上午

Top #2

Rocky Huber

My DZynSource Mold Engineering Software included an injection time calculator, and a mold cooling estimator. The open and close time are very much machine dependent, so I did not include those. The Husky molding machine, and a few others, can open and close much quicker than some other machines.

We, at Ivanhoe, had a mold that we built 20 years ago moved from an older molding machine into a new Husky machine. Nothing else changed. The mold ran about 10 seconds faster in the Husky.

If you send me your part geometry, I'll run it through my software and tell you what I come up with.

08-10-2014 05:09 上午

Top #3

Rick Bakke

Gini,
It's not that complicated. Do you know the weight of the part or volume of the part? You already indicated you have the wall section. Send me some informaiton on the part and I can try to help you out.

08-10-2014 07:24 上午

Top #4

Argini Psymouli

Hello ,

So i have calculated the projected area at 0.036m2 (the general dimensions are 407.68mm x 115.50mm) ; with a general t2.5 and a b srf with many ribs for structural purposes.

The mass estimage (if using ABS with density of 1.05) is 127g .

My image is two symmetrical parts with a 1+1 mould

I would appreciate your help.

Thanks, Gini.

08-10-2014 09:26 上午

Top #5

Steve Thibeault

The ballman-shusman equation provides a reasonably accurate cooling time estimation. The following paper gives the equation and definitions for the terms in the equation:
http://kazmer.uml.edu/staff/Archive/2007_ANTEC_Mold_Design.pdf

08-10-2014 11:39 上午

Top #6

Vicky Teng

so , what the product height ? also is it cold runner or hot runner ? er,,you would try to have a moldflaw, for the molding time will be precision almostly ...

08-10-2014 01:19 下午

Top #7

Charles Beck

The above comments are all correct. I still feel an overview perspective might be useful. Skilled molding professionals can give a very good estimated cycle, although all of us have made significant errors doing this.

The cycle time is a sum. (The time to fill the mold) plus (the time to cool the part {in general this is the longest and most complicated segment, it can be estimated from the wall section, as Steve said, unless there is a physical limitation in the mold which limits the effectiveness of the mold's cooling}) Plus (the time to open the mold, eject or extract the part) (remember to add robot cycle time if one is used) and reclose the mold. Allow time for any core pull or unscrewing mechanism. Having an operator open the gate and remove the part or do anything manual in the mold will make the cycle slow and unpredictable.

If the mold has a runner the time to cool and or remove the runner may cause a significant change in the cycle, particularly if the runner is much thicker than the part, as is often the case. Optimizing runner design is still often overlooked.

The more details known of the part, mold and machine the better estimate can be provided.

08-10-2014 04:03 下午

Top #8

Aw Keng Shing

Depends on how accurate we need to result. In many occasion we are estimating the part price at the beginning of the project where we only have the preliminary part break. We only the part wall thickness and the dimension/cosmetic requirement to estimate the cycle time. We will assume that the cooling channel and gating is well design.

We adjust the figure with different molder because they have different skill and machine.

For sure the calculation is over simplified, but it serve us quite well for preliminary product cost estimation.

08-10-2014 10:11 下午

Top #9

Marcio Santucci

Hi Gini!
Just a add some One more comment... after so many valid comments. We use to call the injection process steps as "wet cycle" for the phases that are non-dependent on the injection machine. On the other hand we have "dry cycle" for the machine times.
A cycle time estimation starts on a collection of all those process phases, from the "wet" to the "dry" times.
I agree with all you have a lot of resources to estimate wet cycle using cae softwares and formulas.
However the key point is must to know what injection machine you have available to produce the part. As a colleague already said there are some machine brands that can provide a very short dry cycle based on high technology on sensoring and control panel, as well simultaneous operations like parallel dosing. This will be determinant to a successful cycle time estimation, a lowest cost part and a reliable process.
Wish you success ... any questions, let me know. BR